Question

Draw a structural formula of the principal product formed when benzonitrile is treated with each reagent. (a) \(\mathrm{H}_{2} \mathrm{O}\) (one equivalent), \(\mathrm{H}_{2} \mathrm{SO}_{4}\), heat (b) \(\mathrm{H}_{2} \mathrm{O}\) (excess), \(\mathrm{H}_{2} \mathrm{SO}_{4}\), heat (c) \(\mathrm{NaOH}, \mathrm{H}_{2} \mathrm{O}\), heat (d) \(\mathrm{LiAlH}_{4}\), then \(\mathrm{H}_{2} \mathrm{O}\)

Short answer

Question: Draw the structural formula of the principal products when benzonitrile is treated with the following sets of reagents: a. H2O (1 equiv) + H2SO4 + heat b. H2O (excess) + H2SO4 + heat c. NaOH + H2O + heat d. LiAlH4, then H2O Answer: a. Benzamide:  b. Benzoic Acid:  c. Benzylamine:  d. Benzylamine: 

Step-by-step solution

In this case, benzonitrile undergoes hydrolysis reaction with the help of one equivalent of water and H2SO4 as a catalyst, in the presence of heat. This reaction generates benzamide as the principal product. The structural formula of benzamide is:  #a(b) H2O (excess) + H2SO4 + heat#

When benzonitrile is treated with excess water and H2SO4 as a catalyst under heat, the nitrile group undergoes hydrolysis twice, first to form benzamide and then to form benzoic acid. The structural formula of benzoic acid is:  #a(c) NaOH + H2O + heat#

Treating benzonitrile with NaOH, H2O, and heat leads to a nucleophilic addition-elimination reaction, which produces benzyl amine (phenylmethanamine) as the principal product. The structural formula of benzyl amine is:  #a(d) LiAlH4, then H2O#

In this scenario, the benzonitrile reacts with LiAlH4, a strong reducing agent, followed by an aqueous work-up. The LiAlH4 reduces the nitrile group to an amine group, again yielding benzyl amine as the principal product. The structural formula of benzyl amine is: